Our sociability correlates with epigenetic oxytocin gene modifications.

From Haas et al.:

 Significance

Elucidating the genetic and biological substrates of social behavior serves to advance the way basic human nature is understood and improves the way genetic and biological markers can be used to prevent, diagnose, and treat people with impairments in social cognition and behavior. This study shows that epigenetic modification of the structural gene for oxytocin (OXT) is an important factor associated with individual differences in social processing, including self-report, behavior, and brain function and structure in humans.

Abstract

Across many mammalian species there exist genetic and biological systems that facilitate the tendency to be social. Oxytocin is a neuropeptide involved in social-approach behaviors in humans and others mammals. Although there exists a large, mounting body of evidence showing that oxytocin signaling genes are associated with human sociability, very little is currently known regarding the way the structural gene for oxytocin (OXT) confers individual differences in human sociability. In this study, we undertook a comprehensive approach to investigate the association between epigenetic modification of OXT via DNA methylation, and overt measures of social processing, including self-report, behavior, and brain function and structure. Genetic data were collected via saliva samples and analyzed to target and quantify DNA methylation across the promoter region of OXT. We observed a consistent pattern of results across sociability measures. People that exhibit lower OXT DNA methylation (presumably linked to higher OXT expression) display more secure attachment styles, improved ability to recognize emotional facial expressions, greater superior temporal sulcus activity during two social-cognitive functional MRI tasks, and larger fusiform gyrus gray matter volume than people that exhibit higher OXT DNA methylation. These findings provide empirical evidence that epigenetic modification of OXT is linked to several overt measures of sociability in humans and serve to advance progress in translational social neuroscience research toward a better understanding of the evolutionary and genetic basis of normal and abnormal human sociability.

Cultural differences in music perception

McDermott et al. find that the isolated Tsimane people, who live in the Amazonian rainforest in northwest Bolivia, have no preference for for consonance over dissonance.

Music is present in every culture, but the degree to which it is shaped by biology remains debated. One widely discussed phenomenon is that some combinations of notes are perceived by Westerners as pleasant, or consonant, whereas others are perceived as unpleasant, or dissonant. The contrast between consonance and dissonance is central to Western music and its origins have fascinated scholars since the ancient Greeks. Aesthetic responses to consonance are commonly assumed by scientists to have biological roots11, and thus to be universally present in humans. Ethnomusicologists and composers, in contrast, have argued that consonance is a creation of Western musical culture. The issue has remained unresolved, partly because little is known about the extent of cross-cultural variation in consonance preferences18. Here we report experiments with the Tsimane’—a native Amazonian society with minimal exposure to Western culture—and comparison populations in Bolivia and the United States that varied in exposure to Western music. Participants rated the pleasantness of sounds. Despite exhibiting Western-like discrimination abilities and Western-like aesthetic responses to familiar sounds and acoustic roughness, the Tsimane’ rated consonant and dissonant chords and vocal harmonies as equally pleasant. By contrast, Bolivian city- and town-dwellers exhibited significant preferences for consonance, albeit to a lesser degree than US residents. The results indicate that consonance preferences can be absent in cultures sufficiently isolated from Western music, and are thus unlikely to reflect innate biases or exposure to harmonic natural sounds. The observed variation in preferences is presumably determined by exposure to musical harmony, suggesting that culture has a dominant role in shaping aesthetic responses to music.

Oxytocin both bonds and divides the sexes.

From Gao et al.:

Facilitation of social attraction and bonding by the evolutionarily conserved neuropeptide oxytocin is well-established in female mammals. However, accumulating behavioral evidence suggests that oxytocin may have evolved sex-specific functional roles in the domain of human social cognition. A critical question is how oxytocin differentially modulates neural processing of social information in men and women, leading to divergent behavioral responses. Here we show that intranasal oxytocin treatment produces sex- and valence-dependent increases in amygdala activation when women view individuals identified as praising others but in men those who criticize them. Women subsequently show increased liking for the faces of these individuals, whereas in men it is reduced. Thus, oxytocin may act differentially via the amygdala to enhance the salience of positive social attributes in women but negative ones in men. We hypothesize that oxytocin may have evolved different but complementary roles to help ensure successful reproduction by encouraging mothers to promote a prosocial rearing environment for offspring and fathers to protect against antisocial influences.

Placebo effects in brain training

Foroughi et al. address the question of whether our desire to become smarter may blind us to the role of placebo effects in brain training regimes. They found that few published articles on cognitive training provide details regarding participant recruitment... whether participants were recruited overtly [e.g., “sign up for a brain training study” ] or covertly [e.g., “did not inform subjects that they were participating in a training study”]. The authors:

...designed a procedure to intentionally induce a placebo effect via overt recruitment. Our recruitment targeted two populations of participants using different advertisements varying in the degree to which they evoked an expectation of cognitive improvement. Once participants self-selected into the two groups, they completed two pretraining fluid intelligence tests followed by 1 h of cognitive training and then completed two posttraining fluid intelligence tests on the following day. Two individual difference metrics regarding beliefs about cognition and intelligence were also collected as potential moderators. The researchers who interacted with participants were blind to the goal of the experiment and to the experimental condition. Aside from their means of recruitment, all participants completed identical cognitive-training experiments. All participants read and signed an informed consent form before beginning the experiment.

Here are their summaries:

Significance

Placebo effects pose problems for some intervention studies, particularly those with no clearly identified mechanism. Cognitive training falls into that category, and yet the role of placebos in cognitive interventions has not yet been critically evaluated. Here, we show clear evidence of placebo effects after a brief cognitive training routine that led to significant fluid intelligence gains. Our goal is to emphasize the importance of ruling out alternative explanations before attributing the effect to interventions. Based on our findings, we recommend that researchers account for placebo effects before claiming treatment effects.

Abstract

Although a large body of research shows that general cognitive ability is heritable and stable in young adults, there is recent evidence that fluid intelligence can be heightened with cognitive training. Many researchers, however, have questioned the methodology of the cognitive-training studies reporting improvements in fluid intelligence: specifically, the role of placebo effects. We designed a procedure to intentionally induce a placebo effect via overt recruitment in an effort to evaluate the role of placebo effects in fluid intelligence gains from cognitive training. Individuals who self-selected into the placebo group by responding to a suggestive flyer showed improvements after a single, 1-h session of cognitive training that equates to a 5- to 10-point increase on a standard IQ test. Controls responding to a nonsuggestive flyer showed no improvement. These findings provide an alternative explanation for effects observed in the cognitive-training literature and the brain-training industry, revealing the need to account for confounds in future research.

Consciousness is the brain messing with itself.

George Johnson does a nice summary of some current ideas on what consciousness is that were discussed at a recent symposium (live stream here) at The New York Academy of Sciences. He notes for example Graziano's ideas that I have previously reviewed on MindBlog:

Descartes’s notion of dualism — mind and body as separate things — has long receded from science. The challenge now is to explain how the inner world of consciousness arises from the flesh of the brain.

Michael Graziano, a neuroscientist at Princeton University, suggested to the audience that consciousness is a kind of con game the brain plays with itself. The brain is a computer that evolved to simulate the outside world. Among its internal models is a simulation of itself — a crude approximation of its own neurological processes... The result is an illusion. Instead of neurons and synapses, we sense a ghostly presence — a self — inside the head. But it’s all just data processing...“The machine mistakenly thinks it has magic inside it,” Dr. Graziano said. And it calls the magic consciousness.

It’s not the existence of this inner voice he finds mysterious. “The phenomenon to explain,” he said, “is why the brain, as a machine, insists it has this property that is nonphysical.”

Johnson notes other ideas aired at the symposium, such as "the centuries-old doctrine of panpsychism — the idea that consciousness is universal, existing as some kind of mind stuff inside molecules and atoms."

Insurance makes sellers of services dishonest.

This piece from Kerschbamer et al. really resonates with my experiences in Florida, scam central for health insurance fraud:

Honesty is a fundamental pillar for cooperation in human societies and thus for their economic welfare. However, humans do not always act in an honest way. Here, we examine how insurance coverage affects the degree of honesty in credence goods markets. Such markets are plagued by strong incentives for fraudulent behavior of sellers, resulting in estimated annual costs of billions of dollars to customers and the society as a whole. Prime examples of credence goods are all kinds of repair services, the provision of medical treatments, the sale of software programs, and the provision of taxi rides in unfamiliar cities. We examine in a natural field experiment how computer repair shops take advantage of customers’ insurance for repair costs. In a control treatment, the average repair price is about EUR 70, whereas the repair bill increases by more than 80% when the service provider is informed that an insurance would reimburse the bill. Our design allows decomposing the sources of this economically impressive difference, showing that it is mainly due to the overprovision of parts and overcharging of working time. A survey among repair shops shows that the higher bills are mainly ascribed to insured customers being less likely to be concerned about minimizing costs because a third party (the insurer) pays the bill. Overall, our results strongly suggest that insurance coverage greatly increases the extent of dishonesty in important sectors of the economy with potentially huge costs to customers and whole economies.

Who blames the victim?

Niemi and Young ask

What determines whether someone feels sympathy or scorn for the victim of a crime? Is it a function of political affiliation? Of gender? Of the nature of the crime? (If you are mugged on a midnight stroll through the park, some people will feel compassion for you, while others will admonish you for being there in the first place. If you are raped by an acquaintance after getting drunk at a party, some will be moved by your misfortune, while others will ask why you put yourself in such a situation.) Their experiments find that the critical factor lies in a particular set of moral values. Their experiments show that the more strongly you privilege loyalty, obedience and purity — as opposed to values such as care and fairness — the more likely you are to blame the victim.

The abstract:

Why do victims sometimes receive sympathy for their suffering and at other times scorn and blame? Here we show a powerful role for moral values in attitudes toward victims. We measured moral values associated with unconditionally prohibiting harm (“individualizing values”) versus moral values associated with prohibiting behavior that destabilizes groups and relationships (“binding values”: loyalty, obedience to authority, and purity). Increased endorsement of binding values predicted increased ratings of victims as contaminated (Studies 1-4); increased blame and responsibility attributed to victims, increased perceptions of victims’ (versus perpetrators’) behaviors as contributing to the outcome, and decreased focus on perpetrators (Studies 2-3). Patterns persisted controlling for politics, just world beliefs, and right-wing authoritarianism. Experimentally manipulating linguistic focus off of victims and onto perpetrators reduced victim blame. Both binding values and focus modulated victim blame through victim responsibility attributions. Findings indicate the important role of ideology in attitudes toward victims via effects on responsibility attribution.

Social support, stress, and the aging brain

Sherman et al. find that the volume of the amygdala in older adults (a center for stress responses) is positively correlated with stress and negatively correlated with social support, these two effects being apparently independent of each other.

Social support benefits health and well-being in older individuals, however the mechanism remains poorly understood. One proposal, the stress-buffering hypothesis states social support ‘buffers’ the effects of stress on health. Alternatively, the main effect hypothesis suggests social support independently promotes health. We examined the combined association of social support and stress on the aging brain. Forty healthy older adults completed stress questionnaires, a social network interview and structural MRI to investigate the amygdala-medial prefrontal cortex circuitry, which is implicated in social and emotional processing and negatively affected by stress. Social support was positively correlated with right medial prefrontal cortical thickness while amygdala volume was negatively associated with social support and positively related to stress. We examined whether the association between social support and amygdala volume varied across stress level. Stress and social support uniquely contribute to amygdala volume, which is consistent with the health benefits of social support being independent of stress.

Is Donald Trump's frontostriatal connectivity weakened?

Chester et al. find an interesting correlation between grandiose narcissism and the strength of connections between brain areas that process self-relevant stimuli (the medial prefrontal cortex) and reward (the ventral striatum):

Narcissism is characterized by the search for affirmation and admiration from others. Might this motivation to find external sources of acclaim exist to compensate for neurostructural deficits that link the self with reward? Greater structural connectivity between brain areas that process self-relevant stimuli (i.e. the medial prefrontal cortex) and reward (i.e. the ventral striatum) is associated with fundamentally positive self-views. We predicted that narcissism would be associated with less integrity of this frontostriatal pathway. We used diffusion tensor imaging to assess the frontostriatal structural connectivity among 50 healthy undergraduates (32 females, 18 males) who also completed a measure of grandiose narcissism. White matter integrity in the frontostriatal pathway was negatively associated with narcissism. Our findings, while purely correlational, suggest that narcissism arises, in part, from a neural disconnect between the self and reward. The exhibitionism and immodesty of narcissists may then be a regulatory strategy to compensate for this neural deficit.

A non-linguistic brain network for mathematics.

From Amalrica and Dehaene:

The origins of human abilities for mathematics are debated: Some theories suggest that they are founded upon evolutionarily ancient brain circuits for number and space and others that they are grounded in language competence. To evaluate what brain systems underlie higher mathematics, we scanned professional mathematicians and mathematically naive subjects of equal academic standing as they evaluated the truth of advanced mathematical and nonmathematical statements. In professional mathematicians only, mathematical statements, whether in algebra, analysis, topology or geometry, activated a reproducible set of bilateral frontal, Intraparietal, and ventrolateral temporal regions. Crucially, these activations spared areas related to language and to general-knowledge semantics. Rather, mathematical judgments were related to an amplification of brain activity at sites that are activated by numbers and formulas in nonmathematicians, with a corresponding reduction in nearby face responses. The evidence suggests that high-level mathematical expertise and basic number sense share common roots in a nonlinguistic brain circuit.

Turning out the vote.

Gilbert Chen summarizes work of Gerber et al.:

A key challenge for any political campaign is to get its voters to actually vote. Field experiments have demonstrated that canvassing and phone calls are more effective than direct mail; all of these interventions increase voter participation by 0.5 to as much as 3 percentage points. With this in mind, Gerber et al. have reexamined an intervention based on the theory that nouns describe more stable attributes than verbs; for instance, “I am a Republican” versus “I vote for Republicans.” They find, using 11,000 voters across three U.S. states, no difference between “noun” and “verb” phone calls and that neither message is as effective as referring to social norms in getting voters to the polls.

Endogenous opioids are not involved in meditation based pain relief

From Zeidan et al.:

Mindfulness meditation, a cognitive practice premised on sustaining nonjudgmental awareness of arising sensory events, reliably attenuates pain. Mindfulness meditation activates multiple brain regions that contain a high expression of opioid receptors. However, it is unknown whether mindfulness-meditation-based analgesia is mediated by endogenous opioids. The present double-blind, randomized study examined behavioral pain responses in healthy human volunteers during mindfulness meditation and a nonmanipulation control condition in response to noxious heat and intravenous administration of the opioid antagonist naloxone (0.15 mg/kg bolus + 0.1 mg/kg/h infusion) or saline placebo. Meditation during saline infusion significantly reduced pain intensity and unpleasantness ratings when compared to the control + saline group. However, naloxone infusion failed to reverse meditation-induced analgesia. There were no significant differences in pain intensity or pain unpleasantness reductions between the meditation + naloxone and the meditation + saline groups. Furthermore, mindfulness meditation during naloxone produced significantly greater reductions in pain intensity and unpleasantness than the control groups. These findings demonstrate that mindfulness meditation does not rely on endogenous opioidergic mechanisms to reduce pain.

The secrets to a long and happy life.

Going through my queue of references that might become mindblog posts I come across this piece by O'Connor, describing findings from the Harvard Study of Adult Development, a research project that since 1938 has closely tracked and examined the lives of more than 700 men and in some cases their spouses.

...one of the most important predictors of whether you age well and live a long and happy life is not the amount of money you amass or notoriety you receive. A much more important barometer of long term health and well-being is the strength of your relationships with family, friends and spouses.

...the study has produced many notable findings. It showed, for example, that to age well physically, the single most important thing you could do was to avoid smoking. It discovered that aging liberals had longer and more active sex lives than conservatives. It found that alcohol was the primary cause of divorce among men in the study, and that alcohol abuse often preceded depression (rather than the other way around).

The people in the strongest relationships were protected against chronic disease, mental illness and memory decline – even if those relationships had many ups and downs...people who sought to replace old colleagues with new friends after retiring were happier and healthier than those who left work and placed less emphasis on maintaining strong social networks...Over and over in these 75 years...the study has shown that the people who fared the best were the people who leaned into relationships with family, with friends and with community.

Why we become more cautious with age.

Rutledge et al. find that the decrease in risk-taking that occurs on aging may be related to dopamine-modulated changes in Pavlovian approach behavior, and not a reduction in the subjective value of incremental rewards as traditional models from economics and psychology would have claimed.

Highlights

•Aging reduced risk taking for potential gains but not potential losses
•Computational models revealed that a Pavlovian influence of reward decreased with age
•Age-related dopamine decline can explain the decrease in Pavlovian biaseswhy we

Summary

The extent to which aging affects decision-making is controversial. Given the critical financial decisions that older adults face (e.g., managing retirement funds), changes in risk preferences are of particular importance. Although some studies have found that older individuals are more risk averse than younger ones, there are also conflicting results, and a recent meta-analysis found no evidence for a consistent change in risk taking across the lifespan. There has as yet been little examination of one potential substrate for age-related changes in decision-making, namely age-related decline in dopamine, a neuromodulator associated with risk-taking behavior. Here, we characterized choice preferences in a smartphone-based experiment (n = 25,189) in which participants chose between safe and risky options. The number of risky options chosen in trials with potential gains but not potential losses decreased gradually over the lifespan, a finding with potentially important economic consequences for an aging population. Using a novel approach-avoidance computational model, we found that a Pavlovian attraction to potential reward declined with age. This Pavlovian bias has been linked to dopamine, suggesting that age-related decline in this neuromodulator could lead to the observed decrease in risk taking.

(You might also check out this article on how monkeys, like humans, become less sociable with age.)

A simple model for why moderate beliefs rarely prevail.

I attend the weekly chaos and complexity seminar at the University of Wisconsin when I am in Madison WI during the summer. I want to pass on the paper by Marvel et al. in Physical Review Letters that was discussed this past week, as well a few clips from a review by Zyga discussing its purely mathematical "model of ideological revolution.":

We live in a world of extremes, where being fervently for or against an issue often becomes the dominant social ideology – until an opposing belief that is equally extreme emerges to challenge the first one, eventually becoming the new social paradigm. And so the cycle repeats, with one ideological extreme replacing another, and neither delivering a sustainable solution. Political revolutions, economic bubbles, booms and busts in consumer confidence, and short-lived reforms such as Prohibition in the US all follow this kind of cycle. Why, researchers want to know, does a majority of the population not settle on an intermediate position that blends the best of the old and new?

The model of ideological revolution begins with a community consisting of four types of individuals: those that currently hold an extreme opinion A, those that hold the opposing extreme opinion B, those that hold neither A nor B (the moderates), and those that hold A indefinitely and never change their minds (the A zealots).

To run the model, two individuals are randomly selected to interact with each other, with one randomly chosen to be the speaker and the other the listener. If the speaker is an A or B and the listener is a B or A, respectively, the speaker changes the listener's beliefs to AB. If the listener is an AB, then the listener becomes an A if the speaker is an A, and becomes a B if the speaker is a B. Moderate speakers cannot change a listener's beliefs; only extremists rally others toward their cause.

Running this basic model, the researchers found that the proportion of zealots strongly affects the outcome. When zealots are below a critical value, the system remains similar to how it started. But above a critical value, the zealots quickly convert the entire population to A...Marvel noted that "a raft of alternatives to our basic model (built from different assumed interactions) all show the same threshold behavior: when the committed believers reach a certain fraction of the community, they are capable of converting everyone to their perspective," Marvel said. "This suggests that a similar threshold may appear in real systems even when those real systems have dynamics somewhat different from our basic model. As the American anthropologist Margaret Mead is claimed to have said, 'Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has.'"

The researchers tested seven different strategies for increasing the moderate subpopulation in the model...only one could effectively expand the moderate subpopulation – and the strategy was based not on social interaction but on other environmental stimuli, which might take the form of a media campaign in real life. By integrating this new parameter into the model, the number of moderates increased without threat of extinction.

"The one successful strategy, nonsocial deradicalization, involves a particularly strong sort of encouragement of moderation; for example, its terms with the new parameter are independent of the size of the moderate population," Marvel said. "Hence, our findings suggest that this strong form of encouragement may be necessary for spreading a balanced perspective in a sustainable way."

The researchers note that this strategy should be regarded with caution, given that they have not attempted to show that the model's dynamics accurately represent the real world, with its multiple small-scale ideologies, fragmentation of opinions, and other intricacies. Nevertheless, they hope that this general framework for testing possible strategies that encourage moderation may lead to the discovery of more sophisticated methods.

The Myth of Cosmopolitanism

I pass on the initial paragraphs of Douthat's excellent Op-Ed piece in Sunday's NYTimes. It it well worth a read:

NOW that populist rebellions are taking Britain out of the European Union and the Republican Party out of contention for the presidency, perhaps we should speak no more of left and right, liberals and conservatives. From now on the great political battles will be fought between nationalists and internationalists, nativists and globalists. From now on the loyalties that matter will be narrowly tribal — Make America Great Again, this blessed plot, this earth, this realm, this England — or multicultural and cosmopolitan.

Well, maybe. But describing the division this way has one great flaw. It gives the elite side of the debate (the side that does most of the describing) too much credit for being truly cosmopolitan.

Genuine cosmopolitanism is a rare thing. It requires comfort with real difference, with forms of life that are truly exotic relative to one’s own. It takes its cue from a Roman playwright’s line that “nothing human is alien to me,” and goes outward ready to be transformed by what it finds.

The people who consider themselves “cosmopolitan” in today’s West, by contrast, are part of a meritocratic order that transforms difference into similarity, by plucking the best and brightest from everywhere and homogenizing them into the peculiar species that we call “global citizens.”

This species is racially diverse (within limits) and eager to assimilate the fun-seeming bits of foreign cultures — food, a touch of exotic spirituality. But no less than Brexit-voting Cornish villagers, our global citizens think and act as members of a tribe.

They have their own distinctive worldview (basically liberal Christianity without Christ), their own common educational experience, their own shared values and assumptions (social psychologists call these WEIRD — for Western, Educated, Industrialized, Rich and Democratic), and of course their own outgroups (evangelicals, Little Englanders) to fear, pity and despise. And like any tribal cohort they seek comfort and familiarity: From London to Paris to New York, each Western “global city” (like each “global university”) is increasingly interchangeable, so that wherever the citizen of the world travels he already feels at home.

The ending lines:

They can’t see that paeans to multicultural openness can sound like self-serving cant coming from open-borders Londoners who love Afghan restaurants but would never live near an immigrant housing project, or American liberals who hail the end of whiteness while doing everything possible to keep their kids out of majority-minority schools.

They can’t see that their vision of history’s arc bending inexorably away from tribe and creed and nation-state looks to outsiders like something familiar from eras past: A powerful caste’s self-serving explanation for why it alone deserves to rule the world.

How exercise enhances brain renewal and growth.

Several studies by now have shown that exercises enhances the production of BDNF (Brain Derived Trophic Factor), which leads to the creation of new nerve cells in the hippocampus (essential for learning and memory - for more on the link of exercise to better mental capacity in older people, see Reynolds.). Sleiman et al. now show that in mice the metabolite β-hydroxybutyrate which increases during heavy exercise induces the activity of BNDF gene promoters. Their detailed abstract:

Exercise induces beneficial responses in the brain, which is accompanied by an increase in BDNF, a trophic factor associated with cognitive improvement and the alleviation of depression and anxiety. However, the exact mechanisms whereby physical exercise produces an induction in brain Bdnf gene expression are not well understood. While pharmacological doses of HDAC inhibitors exert positive effects on Bdnf gene transcription, the inhibitors represent small molecules that do not occur in vivo. Here, we report that an endogenous molecule released after exercise is capable of inducing key promoters of the Mus musculus Bdnf gene. The metabolite β-hydroxybutyrate, which increases after prolonged exercise, induces the activities of Bdnf promoters, particularly promoter I, which is activity-dependent. We have discovered that the action of β-hydroxybutyrate is specifically upon HDAC2 and HDAC3, which act upon selective Bdnf promoters. Moreover, the effects upon hippocampal Bdnf expression were observed after direct ventricular application of β-hydroxybutyrate. Electrophysiological measurements indicate that β-hydroxybutyrate causes an increase in neurotransmitter release, which is dependent upon the TrkB receptor. These results reveal an endogenous mechanism to explain how physical exercise leads to the induction of BDNF.

Cognitive fatigue increases impulsivity.

Sort of makes sense..Blain et al. show that if you use your lateral prefrontal cortex (LPFC) for control process required for an extended intense workday, its function in resisting the temptation of immediate rewards is diminished, you're more likely to eat that late afternoon sugar roll. Their abstract:

The ability to exert self-control is key to social insertion and professional success. An influential literature in psychology has developed the theory that self-control relies on a limited common resource, so that fatigue effects might carry over from one task to the next. However, the biological nature of the putative limited resource and the existence of carry-over effects have been matters of considerable controversy. Here, we targeted the activity of the lateral prefrontal cortex (LPFC) as a common substrate for cognitive control, and we prolonged the time scale of fatigue induction by an order of magnitude. Participants performed executive control tasks known to recruit the LPFC (working memory and task-switching) over more than 6 h (an approximate workday). Fatigue effects were probed regularly by measuring impulsivity in intertemporal choices, i.e., the propensity to favor immediate rewards, which has been found to increase under LPFC inhibition. Behavioral data showed that choice impulsivity increased in a group of participants who performed hard versions of executive tasks but not in control groups who performed easy versions or enjoyed some leisure time. Functional MRI data acquired at the start, middle, and end of the day confirmed that enhancement of choice impulsivity was related to a specific decrease in the activity of an LPFC region (in the left middle frontal gyrus) that was recruited by both executive and choice tasks. Our findings demonstrate a concept of focused neural fatigue that might be naturally induced in real-life situations and have important repercussions on economic decisions.

The brain makes maps of abstract realms.

Underwood summarizes the importance of recent work by Constantinescu et al.

The brain is a mapmaker. As you navigate a landscape, neurons in a region called the entorhinal cortex fire at multiple locations, marking out a hexagonal grid on a mental map. The discovery of these so-called grid cells, and their role as a neuronal GPS for spatial navigation, won the 2014 Nobel Prize in Physiology or Medicine for Norwegian scientists Edvard Moser and May-Britt Moser. Now, it seems that the brain may make maps of abstract realms, too. A team at the University of Oxford in the United Kingdom provides evidence that gridlike neuronal activity throughout the brain helps people organize nonnavigation knowledge—for the purposes of the new study, differences in body shape between various types of birds. Several brain regions, including the entorhinal cortex and the ventromedial prefrontal cortex, showed gridlike neural representation of conceptual space.

The abstract of the article:

It has been hypothesized that the brain organizes concepts into a mental map, allowing conceptual relationships to be navigated in a manner similar to that of space. Grid cells use a hexagonally symmetric code to organize spatial representations and are the likely source of a precise hexagonal symmetry in the functional magnetic resonance imaging signal. Humans navigating conceptual two-dimensional knowledge showed the same hexagonal signal in a set of brain regions markedly similar to those activated during spatial navigation. This gridlike signal is consistent across sessions acquired within an hour and more than a week apart. Our findings suggest that global relational codes may be used to organize nonspatial conceptual representations and that these codes may have a hexagonal gridlike pattern when conceptual knowledge is laid out in two continuous dimensions.

Training our brains without our awareness.

There is growing interest in the use of neurofeedback (NF) as a tool to study and treat various clinical conditions. The uses of NF are diverse, ranging across a variety of motor and sensory tasks, investigation of cortical plasticity and attention, to treatment of chronic pain, depression, and mood control. In NF studies participants are typically aware that they are being trained, and received specific goals for this training. Ramos et al. take the important step of showing that targeted brain networks can be modulated even in the complete absence of participants' awareness that a training process is taking place. From their introduction:

...participants were informed that they were engaged in a task aimed at mapping reward networks. Unbeknownst to them, these rewards were coupled with fMRI activations in specific cortical networks. Participants received auditory feedback associated with positive and negative rewards, based on blood oxygen level-dependent (BOLD)–fMRI activity from two well-researched visual regions of interest (ROIs), the fusiform face area (FFA) and the parahippocampal place area (PPA). However, participants were not informed of this procedure and believed, as revealed also by postscan interviews and questionnaires, that the reward was given at random.

They found that 10 of 16 participants were indeed able to modulate their brain activity to enhance the positive rewards, and were completely unaware that they were doing this. This ability was associated with changes in connectivity that were apparent in post-training rest sessions, indicating that the network changes resulting from the training carried over beyond the training period itself. The authors point out:

...that brain networks can be modified even in the complete absence of intention and awareness of the learning situation, raising intriguing possibilities for clinical interventions.